A virtual-real combined bearing dynamic thermal resistance measurement method

Abstract

The application discloses a kind of bearing dynamic thermal resistance determination methods of virtual and real combination, comprising: experimental part, comprising: power to temperature constant, record bearing inner and outer ring surface temperature, by the power shown by metering socket, calculate bearing static radial thermal resistance according to formula;Simulation part: bearing geometric model is simplified, and the multiphase flow simulation model of bearing lubrication and heat transfer is established;In simulation model, set up multiple reference system for bearing inner and outer ring and ball, set up heat insulation on the two sides of bearing, inner and outer ring surface temperature is fixed value, simulate radial heat transfer;Monitoring inner and outer ring surface heat flow and calculating thermal resistance, adjust the volume ratio of lubricating grease in bearing cavity at very low speed until the thermal resistance value is equal to the experimental value, to calibrate bearing simulation model;Different rotational speed is set to bearing, and the thermal resistance under different rotational speed and lubricating grease distribution can be calculated.According to the technical scheme of the application, the simulation result has good precision, and the thermal resistance value of bearing under different rotational speed conditions can be accurately simulated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bearing performance testing, and particularly relates to a virtual-real combined bearing dynamic thermal resistance determination method. BACKGROUND

[0002] As a key support and rotating component in mechanical equipment, the thermal performance of bearings has a crucial influence on the overall operation state of the equipment. However, the existing bearing thermal resistance determination methods have many limitations and shortcomings.

[0003] Theoretical calculation methods are often based on simplified model structures and idealized assumption conditions, and it is difficult to comprehensively consider the bearing lubricating medium and working condition. For example, under actual working conditions, the distribution of lubricating grease and the temperature gradient distribution are complex and variable, which are often simplified or ignored in the theoretical calculation model, resulting in a large deviation between the calculation results and the actual thermal resistance. Simulation is also one of the commonly used methods for calculating the thermal resistance of bearings, but since grid deformation needs to be realized to adapt to the fluid boundary of rapid movement in the simulation of multiphase flow of lubricating state, convergence problems are often encountered in CFD simulation. Whether theoretical calculation or numerical simulation, the results need to be verified by experiments.

[0004] However, experimental measurement methods also face many challenges and limitations. Traditional contact temperature sensors, such as thermal resistors or thermocouples, can accurately measure the temperature of the bearing outer ring, but are not suitable for the inside of the bearing, and the measurement of the inner ring temperature also requires special connecting devices such as slip rings. Inductive coupling type wireless temperature sensors are susceptible to signal interference and have short coupling distance. Fiber Bragg grating sensors can measure the temperature inside the bearing, but also face challenges such as wiring difficulties and complex demodulation equipment.

[0005] More importantly, most of the existing bearing thermal resistance determination methods lack effective coordination and deep integration between experiments and simulations. Experiments can provide accurate data, but have limitations in analyzing the internal heat transfer mechanism of the bearing and are difficult to implement; simulation can simulate various complex situations, but needs experimental data for verification and calibration to ensure the accuracy of the model. Therefore, there is an urgent need for an innovative bearing thermal resistance determination method that combines the respective advantages of experiments and simulations. This virtual-real combined method can ensure the accuracy of bearing thermal resistance determination while reducing the difficulty of experimental implementation and improving the understanding of the heat transfer mechanism. SUMMARY

[0006] The core of the present application is to overcome the limitations of the prior art, provide a comprehensive, combined with the bearing thermal resistance confirmation method of experiment and simulation, realize the high precision determination of bearing thermal resistance, especially can accurately grasp the change rule of bearing thermal resistance under different working conditions, provide solid technical support for the optimization design, performance improvement and reliable application of bearing in various mechanical equipment.

[0007] According to the technical scheme of the present application, a virtual-real combined bearing dynamic thermal resistance determination method is provided, comprising the following steps:

[0008] The experimental part comprises:

[0009] The thermocouple is pasted on the inner and outer ring surfaces of the bearing, the heat preservation and insulation material is pasted on the two end surfaces of the bearing, the heat-conducting silicon grease is uniformly coated on the inner and outer ring surfaces of the bearing, the heating ring is sleeved on the outer ring surface of the bearing and fixed, and the bearing is installed on one end of the expansion shaft;

[0010] The temperature is kept constant by power supply, and the temperature of the inner and outer ring surfaces of the bearing is recorded, the power is calculated by the metering socket data, and the formula is used to calculate the bearing static radial thermal resistance, wherein The thermal resistance is calculated, wherein The temperature difference between the inner and outer ring surfaces is The heating power is

[0011] The simulation part comprises:

[0012] The three-dimensional model of the bearing is drawn or downloaded, the three-dimensional model of the bearing is simplified, the material properties are set according to the manufacturer's data, and the multiphase flow simulation model of bearing lubrication and heat transfer is established;

[0013] The inner and outer rings and the balls in the multiphase flow simulation model are set with multiple reference systems;

[0014] The two side surfaces of the multiphase flow simulation model are set to be heat-insulated, the inner and outer ring surface temperatures are set to be fixed values, and the heat is transmitted along the radial direction of the bearing;

[0015] The heat of the inner and outer ring surfaces is monitored, the thermal resistance is calculated, the volume ratio of the lubricating grease in the bearing cavity is adjusted at a speed lower than 10 revolutions per minute until the simulation calculated thermal resistance value is equal to the measured static thermal resistance value, so as to calibrate the multiphase flow simulation model;

[0016] The bearing is set to different rotating speeds in the multiphase flow simulation model, and the thermal resistance under different rotating speeds is calculated.

[0017] Advantages:

[0018] ​Since the static thermal resistance measurement result of the bearing is used to calibrate the CFD simulation model, the simulation result has good accuracy and can accurately simulate the thermal resistance value of the bearing under different rotating speeds. The method disclosed by the application is easy to implement, eliminates the dependence on complex measuring devices while ensuring the accuracy of bearing thermal resistance measurement, effectively reduces the experimental cost, and has a wide application prospect in the field of transmission system thermal management technology with high-speed bearings. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A flowchart of the virtual-real combined bearing dynamic thermal resistance measurement method provided by the embodiment of the application is shown in

[0020] Figure 2 A general diagram of the experimental device is shown in

[0021] Figure 3 A bearing local diagram of the experimental device is shown in

[0022] Figure 4 A multi-reference frame (MRF) modeling schematic diagram is shown in

[0023] Figure 5 A bearing grease distribution diagram under 3000 rpm is shown in

[0024] Figure 6 A bearing thermal resistance under different rotating speeds is shown in DETAILED DESCRIPTION

[0025] Figure 1 A flowchart of the virtual-real combined bearing dynamic thermal resistance measurement method provided by the embodiment of the application is shown in Figure 1 As shown in the figure, the method comprises:

[0026] An experimental part, the device of which is shown in Figure 2 Comprises:

[0027] Paste the patch type thermocouple on the inner and outer ring surfaces of the bearing, paste the heat preservation and insulation material on the two end surfaces of the bearing, uniformly coat the heat-conducting silicone grease on the inner and outer ring surfaces of the bearing, as shown in Figure 3

[0028] Wrap the heating ring on the outer ring surface of the bearing and fix it, and install the bearing on one end of the expansion shaft;

[0029] Conduct electricity to constant temperature, record the temperature of the inner and outer ring surfaces of the bearing, calculate the power from the metering socket data, and calculate the bearing static radial thermal resistance according to the formula , wherein is the thermal resistance, is the temperature difference between the inner and outer ring surfaces, is the heating power;

[0030] Simulation part: ​

[0031] A bearing three-dimensional model is drawn or downloaded, the bearing three-dimensional model is simplified, material properties are set according to manufacturer data, and a multiphase flow simulation model of bearing lubrication and heat transfer is established;

[0032] In the multiphase flow simulation model, multiple reference systems are set for the inner and outer rings and the rolling balls of the bearing, as shown in the following table: Figure 4 The rotational speeds of the reference systems are as follows:

[0033]

[0034]

[0035]

[0036] In the formula, is the rotational speed of the bearing, is the diameter of the rolling ball, is the pitch diameter of the bearing, and are the rotational speeds of the inner ring reference system, the outer ring reference system, and the reference system of each rolling ball, respectively.

[0037] In the multiphase flow simulation model, the two sides are set to be adiabatic, and the inner and outer ring surfaces are set to have fixed temperatures, so that heat is transferred along the radial direction of the bearing;

[0038] The heat of the inner and outer ring surfaces is monitored to calculate the thermal resistance, and the volume ratio of the lubricating grease in the bearing cavity is adjusted at a rotational speed of less than 10 rpm until the simulated thermal resistance value is equal to the measured static thermal resistance value, thereby calibrating the multiphase flow simulation model.

[0039] In the multiphase flow simulation model, the bearing is set to have different rotational speeds, and the thermal resistance at different rotational speeds is calculated.

[0040] Figure 5 is the distribution diagram of the inner lubricating grease of the bearing at 3000 rpm. Figure 6 is the thermal resistance of the bearing at different rotational speeds.

[0041] In the experimental part, high-temperature insulation materials are used, which are cut and pasted on the end surface of the bearing for insulation to reduce axial heat loss.

[0042] In the experimental part, an expansion shaft is used to install the bearing to ensure close contact between the bearing and the shaft, so as to ensure effective heat transfer. The shaft is a conventional component in the art, and the bearing is used to support and fix the shaft.

[0043] In the experimental part, the outer ring of the bearing is heated by an electric heating ring, and the inner ring of the bearing is cooled by an expansion shaft, which is cooled by ice water to provide constant temperature cooling conditions.

[0044] ​​Wherein, the outer ring is a bearing component, the outer ring surface is the ring surface of the bearing outer ring (also the radially outermost surface of the bearing). The inner ring is also a bearing component, and the "inner ring surface" is the ring surface of the bearing inner ring (also the radially innermost surface of the bearing).

[0045] In the simulation part, the multi-reference system dynamic-static method is adopted, including: creating a rotating reference system for the bearing inner and outer rings and the rolling balls, and the rotating speeds are respectively:

[0046]

[0047]

[0048]

[0049] In the formula, is the rotating speed of the bearing, is the diameter of the rolling ball, is the pitch diameter of the bearing, and , , are the rotating speeds of the bearing inner ring reference system, the bearing outer ring reference system, and each rolling ball reference system, respectively.

[0050] In the simulation part, the bearing three-dimensional model calibration includes: comparing the simulated heat resistance value at a rotating speed below 10 revolutions per minute with the measured static heat resistance value, and eliminating the deviation between the simulation result and the measured value by fine-tuning the volume ratio of lubricating grease or other key model parameters that cannot be accurately determined, to complete the bearing three-dimensional model calibration.

[0051] An example is described below.

[0052] 1. Experimental part

[0053] 1) Experimental material preparation:

[0054] Ice water bucket: Choose an iron bucket or a wooden bucket with appropriate capacity, avoid using plastic buckets with poor heat resistance, and use ice water mixture to maintain constant cooling temperature.

[0055] Expansion shaft: Choose a stainless steel expansion shaft with appropriate diameter range for installing and fastening the measured bearing.

[0056] Heat insulation support frame: design a suitable support frame with clamps made of materials with good heat insulation performance for fixing the expansion shaft.

[0057] Electric heating ring: can be fastened on the outer ring surface of the bearing to achieve uniform heating.

[0058] Power supply: choose a power supply or metering socket that can accurately set the output power.

[0059] Thermometer: with multi-channel acquisition function, equipped with thin film thermocouple or thermal resistance.

[0060] Thermal silicone grease and high-temperature glue: required to be suitable for the temperature range of the experiment.

[0061] Thermal insulation material: choose high-temperature-resistant thermal insulation material tape for the bearing end face to avoid axial heat loss.

[0062] Protective gloves: choose high-temperature-resistant and anti-scald gloves to ensure safety.

[0063] 2) Experimental device assembly:

[0064] Paste thin film thermocouple or thermal resistance: first clean the inner and outer ring surfaces of the bearing thoroughly to ensure the surface is clean; then use high-temperature glue to firmly paste the thin film thermocouple or thermal resistance on the inner and outer ring surfaces of the bearing, and gently press to ensure that there is no air bubble between the contact surfaces; finally, evenly apply thermal silicone grease on the inner and outer ring surfaces of the bearing.

[0065] Install the heating ring: put the heating ring on the outer ring surface of the bearing and clamp it tightly to ensure that the heating ring covers and tightly fits the entire outer ring surface of the bearing.

[0066] Install the bearing: put the inner ring of the bearing in the middle of the expansion shaft and tighten the expansion shaft so that there is no gap between the inner ring of the bearing and the contact surface.

[0067] Paste thermal insulation material: cut the thermal insulation material tape and paste it on the bearing end face to ensure that it fits neatly with the bearing end face; maximize the prevention of heat loss from the bearing end face.

[0068] Fix the expansion shaft: use the thermal clamp of the support frame to clamp one end of the expansion shaft to make it stand upright and fixed, and the other end of the expansion shaft extends into the ice water bucket.

[0069] Connect the power supply and thermometer: connect the thin film thermocouple or thermal resistance pasted on the bearing to the thermometer; under the condition of disconnecting the power supply, connect the heating ring wire to the power supply device or metering socket.

[0070] 3) Data measurement and recording:

[0071] Pre-power check: before turning on the power, check all experimental equipment to ensure correct and firm connection. Especially check whether the installation of the bearing, heating ring, expansion shaft and support is firm, whether the connection of the heating ring and the power supply is safe and correct, and whether the thermometer with thermocouple or thermal resistance connected correctly displays the reading.

[0072] Temperature monitoring and recording: After the heating ring is powered on, the experimenter needs to closely monitor the temperature change displayed by the temperature monitor, and prevent the temperature from rising too high by adjusting the heating power. Record the temperature data of the inner and outer ring surfaces of the bearing in a timely manner. When the temperature remains unchanged for several consecutive minutes, it can be determined that the bearing has reached thermal equilibrium.

[0073] Power calculation and recording: After the bearing temperature stabilizes, record the heating power data displayed on the power supply or metering socket to obtain accurate heating power.

[0074] Thermal resistance bearing calculation: According to the formula Calculate the static thermal resistance of the bearing, where is the thermal resistance between the inner and outer ring surfaces of the bearing, is the temperature difference between the inner and outer ring surfaces, is the heating power.

[0075] 2. Simulation section

[0076] 1) Bearing model simplification and error elimination

[0077] In the geometric creation of the simulation model, appropriate simplification can be made, the bearing support frame can be removed, and the clearance of each ball and the inner and outer raceways can be kept the same. The overall error of the model caused by geometry, boundary condition simplification and other uncertain factors can be eliminated in the subsequent model calibration by adjusting a single model parameter.

[0078] 2) Dynamic and static modeling of bearing rotation

[0079] Based on the multi-reference frame (MRF) dynamic and static method, a rotating reference coordinate system is created for the inner and outer rings and the balls of the bearing, as shown in Figure 4 The rotation speeds of each reference system are set as follows:

[0080]

[0081]

[0082]

[0083] In the formula, is the bearing rotation speed, is the ball diameter, is the bearing pitch diameter, and , , are the rotation speeds of the inner ring reference system, the outer ring reference system and each ball reference system, respectively.

[0084] In the simulation model, appropriate rotating reference systems are set for each fixed component area, and the same rotating reference system as the contacted solid is set for each boundary of the fluid area.

[0085] 3) Thermal boundary conditions of bearing model

[0086] In line with the insulation treatment of experimental measurement, the axial two end faces of the bearing model are set as adiabatic boundary conditions. The annular surfaces of the inner and outer rings of the bearing are set as fixed temperature boundary conditions.

[0087] 4) Thermal resistance calculation and model correction

[0088] Thermal resistance calculation: In the simulation, the heat flow curves of the annular surfaces of the inner and outer rings are monitored in real time over time. When the simulation reaches thermal equilibrium, the heat flow of the annular surfaces of the inner and outer rings tends to be stable and substantially equal. The total radial thermal resistance of the bearing is obtained by dividing the temperature difference set for the annular surfaces of the inner and outer rings by the stable heat flow.

[0089] Model calibration: The thermal resistance simulation calculation results at extremely low speed are compared with the static experimental measurement results. By fine-tuning the grease volume ratio or other key model parameters that cannot be accurately determined, the deviation between the simulation results and the measured values is eliminated, and the model calibration is completed.

[0090] 4) Simulation of different working conditions

[0091] According to the set speed, the appropriate time step is selected for the simulation calculation of the thermal resistance at different speeds, and the curve of the thermal resistance changing with the speed is drawn.

[0092] In summary, at present, the widely used experimental measurement method of bearing thermal resistance needs to use wireless sensing or slip ring to arrange temperature sensors for the moving parts of the bearing, which is very difficult to implement. The numerical simulation method needs to be confirmed by experiments for its accuracy, and the multiphase flow simulation of the grease is also difficult to converge due to the existence of moving parts. The present application adopts a virtual-real combined scheme: first, a simple device is used to measure and obtain the static thermal resistance of the bearing in the experimental link; then, a multiphase flow computational fluid dynamics (CFD) thermal simulation model of the bearing is established, and the static simulation of the bearing movement is realized based on the moving static method of multiple reference frames (MRF). Since the CFD simulation model is calibrated based on the static thermal resistance measurement results of the bearing, the simulation results have good accuracy and can accurately simulate the thermal resistance values of the bearing under different speed conditions. The method disclosed in the present application is easy to implement, ensures the accuracy of the bearing thermal resistance measurement, eliminates the dependence on complex measurement devices, effectively reduces the experimental cost, and has a wide application prospect in the field of thermal management technology of transmission systems with high-speed bearings.

Claims

1. A method for determining the dynamic thermal resistance of bearings using a combination of real and virtual methods, characterized in that, The method comprises the following steps: The experimental part comprises: A thermocouple is attached to the inner and outer ring surfaces of the bearing, and heat insulation materials are attached to the two end surfaces of the bearing. The inner and outer ring surfaces of the bearing are uniformly coated with heat-conducting silicone grease. A heating ring is sleeved on the outer ring surface of the bearing and fixed. The bearing is mounted on one end of the expansion shaft. The inner and outer ring surface temperature of the bearing is recorded while the power is kept constant, the power is calculated from the meter socket data, and the formula The static radial thermal resistance of the bearing is calculated, wherein is the thermal resistance, is the temperature difference between the inner and outer ring surfaces, is the heating power; The simulation part: Draw or download the three-dimensional model of the bearing, simplify the three-dimensional model of the bearing, set the material properties according to the manufacturer's data, and establish a multiphase flow simulation model of bearing lubrication and heat transfer. Set multiple reference systems for the inner and outer rings and the balls in the multiphase flow simulation model. Set the two side surfaces of the multiphase flow simulation model as adiabatic, and set the inner and outer ring surface temperatures as fixed values, so that heat is transferred along the radial direction of the bearing. Monitor the heat flow of the inner and outer ring surfaces to calculate the thermal resistance. Adjust the volume ratio of the lubricating grease in the bearing cavity at a speed lower than 10 rpm until the simulation calculated thermal resistance value is equal to the measured static thermal resistance value, thereby calibrating the multiphase flow simulation model. Set different speeds for the bearing in the multiphase flow simulation model and calculate the thermal resistance at different speeds.

2. The hybrid bearing dynamic thermal resistance determination method of claim 1, wherein, The heat insulation material is a high-temperature resistant insulation material tape, which is cut and attached to the end surface of the bearing for heat insulation.

3. The hybrid bearing dynamic thermal resistance determination method of claim 1, wherein, Mounting the bearing on one end of the expansion shaft includes ensuring close contact between the bearing and the shaft.

4. The hybrid bearing dynamic thermal resistance determination method of claim 1, wherein, The outer ring of the bearing is heated by an electric heating ring, and the inner ring of the bearing is cooled by an expansion shaft.

5. The hybrid bearing dynamic thermal resistance determination method of claim 1 wherein, Ice water is used to provide constant temperature cooling conditions for the expansion shaft.

6. The hybrid bearing dynamic thermal resistance determination method of claim 1 wherein, The simulation model uses the multi-reference system dynamic and static method to create rotating reference systems for the inner and outer rings and the balls of the bearing, with rotating speeds of: wherein is the bearing rotational speed, is the ball diameter, is the bearing pitch diameter, and , , are the rotational speeds of the bearing inner ring reference frame, the bearing outer ring reference frame, and each ball reference frame, respectively.

7. The hybrid bearing dynamic thermal resistance determination method of claim 1 wherein, The bearing lubrication and heat transfer simulation model calibration includes: comparing the simulation calculated thermal resistance value at a speed lower than 10 rpm with the measured static thermal resistance value, adjusting the volume ratio of the lubricating grease, eliminating the deviation between the simulation results and the measured values, and completing the model calibration.

Images